This invention pertains to mechanical elements of electrochemical batteries, and, more particularly, is concerned with an element for use in bipolar plate-type batteries.
As is well known, a battery includes a plurality of cells arranged in series to provide a voltage greater than that possible from a single cell alone. One type of electrochemical cell employs a reducible liquid cathode and includes a lithium anode, a carbon cathode structure, and a porous separator interposed between the lithium anode and the carbon current collector cathode structure. The assembly of the lithium anode, carbon cathode current collector structure and separator is exposed to an electrolytic solution including a reducible liquid cathode and a dissolved electrolyte solute. Suitable materials for the reducible liquid cathode are thionyl chloride and sulfonyl chloride. The electrolyte solute may be lithium tetrachloraluminate for example.
Furthermore, it is known that the anode and cathode current collector structure of adjacent cells may be on opposite sides of a conductive carrier plate or substrate. The assembly is called a bipolar plate.
A battery can be made with a multiplicity of bipolar plates arranged in a stack with the ends of the stack terminated by plates carrying either an anode or a cathode current collector structure. An insulation or separator made of a thin porous material such as a fiberglass sheet (glass paper) is interposed between facing anode and cathode current collector structures. A quantity of electrolyte solution is carried between the plates. The elements and electrolyte between adjacent carrier plates form a cell. Adjacent cells are connected in series through the carrier plates. To prevent short circuits between cells, it is important that the various plates be electrically insulated from each other, and that there is no communication of electrolyte solution between cells.
At the same time, the plates must be mechanically supported in their relative positions during normal and shock conditions.
In the above cited copending application, a method of assembly plates into a battery stack was disclosed in which frames are placed between plates. The frames overlap the periphery of the plates and are fused together to form a unified battery housing. This has been found to be an excellent method; however, care must be taken to assure alignment of plates and the flexible separators during assembly.